Wireless communications devices are an integral part of society and permeate daily life. The typical wireless communications device includes an antenna, a transceiver coupled to the antenna, and an audio output/input device. The transceiver and the antenna cooperate to transmit and receive communications signals. A typical wireless communications device includes a power amplifier for amplifying low amplitude signals for output via an audio output device, such as a speaker, for example.
In the typical wireless communications device, the audio performance of the speaker can be limited. This is generally due to the low power amplifier and the size of the speaker. Indeed, in mobile applications, these restraints on design are quite pronounced. Also, a voice based audio output signal may be difficult to process due to its high peak-to-average ratio. Because of this, the typical mobile wireless communications device may provide audio output with significant distortion, which is undesirable.
An approach to this issue is to compress the audio output signal before outputting via the speaker. In short, the compression reduces the level of the loudest signals in the audio output signal. Two facets of the audio output signal that can be regulated are the peak levels of the signal and the dynamic range of the signal.
In particular, some approaches use a fixed compression algorithm. These compression algorithms have a fixed gain where higher voltages have less gain than lower voltages. Also, the gain does not vary over time in these approaches. Other approaches use dynamic compression algorithms. These dynamic algorithms include an attack time, i.e. a time needed to attenuate the audio output signal, and a release time, i.e. a time needed to return the audio output signal to original form.
For example, U.S. Pat. No. 8,750,525 to Martz et al., also assigned to the present application's assignee, the contents of which are hereby incorporated by reference in their entirety, discloses a dynamic compression algorithm approach. Nevertheless, dynamic algorithm approaches typically cannot guarantee a peak limit and may be difficult to tune, thereby giving each device a different sound or tonality.
Also, U.S. Pat. No. 8,983,092 to Thormundsson et al. discloses another approach. This approach includes a dynamic range compressor/peak limiter comprising a look-ahead buffer and an analysis engine. The look-ahead buffer holds a window of samples of a signal. The analysis engine selects a gain envelope function on the basis of the samples by selecting the Pth sample in the buffer whenever that sample exceeds a given threshold.